Add: stackcollapse.py converter to Folded Stacks

This converts to Brendan Gregg's Folded Stack Format:
https://queue.acm.org/detail.cfm?id=2927301#:~:text=The%20folded%20stack%2Dtrace%20format,trace%2C%20followed%20by%20a%20semicolon.

This tries to be consistent with
https://github.com/brendangregg/FlameGraph/blob/master/stackcollapse-perf.pl,
outputting annotations for kernel and JIT code for colour-coding in
flamegraph.pl downstream.

BUG=201571852

Change-Id: I9083299f5662f87d059b5881d5127e23dbe9e7e3
Test: Ran test/test.py -p TestStackCollapse.\*
13 files changed